Rubber



I phatic' and aromati' organic Patented Oct. 5, 1943 UNITED STATES Connecticut if No Drawing. Original application-October 21,

l 1937, Serial No.170,194. Divided and this am. a f ,1

,lplicationiJulyulll, 1940, SerialNo'.i346,326.

' f 50mins; lollecqgis'si r droloromic."acid; hydrofluoric acidl' acetic; acid,

formic; acid; lactic acid, glycolic acid} butryrica This invention relates to improvements in rubber' compounding. It includes new and improved rubber compositions,as well as processes by which theymay be produced. This application is azdivi sion of our prior application Serial No. 170,194, P5

filed October 21, 1937; now Patent No. 2,210,763.

In accordancewith'the present invention; impingementcarbon blacks, treated witha small amount of an acid are incorporated in rubber om t r i ul nrlr t ead st k com o t -v The car o black 9 use -ar th s '6 f 'cr' ed n cia medi n our a r-x 6 a p t o Such carbon blacks arefniade apt; exceedingly 'fine particles, andan exceedingly la number th e am e 1 s,: w it-@912 t e a iafacture' of rubber *c' mpos gmnsgcpntamm them. I The diiiiculty in obtaining a s mc e uy uniform distributionjand' dispersion Ifo'i j't'h e carbon black particles in the rubber compositions in" which acid, benzoic acid, maleic acid, propionics'acid, salicylic acid; acetylvl salicyli'c acidpmonochlon acetic acid, dichloracetic acid, trichfloracetic acid,

' and'phthalic acid. l a a l solutionnor in some-casesixi solutionrinwone ofthe lower alcohols; 0 When alcohol solutions are used they should in general be'freshlyprepared to avoidesterificationioffkthe alcohol 1' withiithe 1 acidbefore use. An aqueous solution oithe-acid oan begisprayed lonto. thevbl'ack 'andxthe. entire mass of black 'then thoroughly. mixedror thefacid. a j. 5 can be added in some casesint'gaseou 'if rm;,b f

a-masteri batch can bemade containing ailarger v amount of acid than. requiredlina the final product and xthisibatch then; admixed (with a: .mass of untreated b1ack,;:with thorough admixture: Il'he'. r

they are used is Well known in the art and Various (2 admixture can advantageouslytake placeat ordii proposals have heretofo ie been' ina such diificultyi tooi/ercomfe The ,improvedftreatedj im blacks used in p jp'racticingthe present invention haveffimproved I pro erties which' facilitate the 'desiredfditribu-ll t n he hrm ghi j'rl i be mi t The acid "which'we have found particularly a va a eo n h t e m t" 161 th 'j'ca it blacks is hydrochloricf acid; in amount representing" only a small fraction "of 1 .01 the" black treated, rqry extmpie; iq-.0592, or 0.1%.; i j I i ot er acids used' iorfltreatin the carbon jibla ks; in u in bo h: mi e acids nd l soluble in waterfandfwhich ca admixed" with the carb'onbla'ck 'to"be'* treated.

I In general, the amounts o f' otherfacids will f vary somewhatjbut for best results only a; fraction of fa percent and usuallyja small fraction'off aper- 1 centgfseems sufiicient; Various acids, in' amount s 4 somewhat larger amounts nfi'aiy lie-useful; "lngen- 5 eraltlie amountofacidrequired w'ill beles'sthan 1%; and for -many -=ifnot mesa acids the best results appear to be obtained withlesstha'n 0. 5 and: amounts as small as 40.01 %'*;have in some of acidcanibe used inzsome casesparticularly inr the case. of some of the organicfacidsndeli; 1;,gAmong the-acids. which canthusbe iusedare included hydrochloric acid; sulphuric acid, sulimproved properties, particularly from :naryy temperatures-and; pressureszrz; ,zWhre :ithe

Vblackis formed intojpellets; the acid can be added I etothewwateriused in 'iorming the pellets.

; ough admixture If subsequent to the; addition of acid; the black'is subjected to heat-:treatment,

.i thetime and temperatureof such'hea'titreatment should be so controlled or adjusted that ithegacid rbo nig -.;isinoti; destr9yed or driven; out; .orri the: treated" V f ublackfso changed asito destroy or.,render:1nefiective the acid treatment. We havezfburidgthat {the Spraying of 1 an acidiontlo. the blackifollow'ed 1 g-by'ithorough admixture and byi permitting the -treatedb1ack tori-stand resuits iniapparentlyiuni-' form and ijthorough dissemination ,roi the-acid I 3 -throughout; the} bla'ckg possibly duehto migration g f orrvapor; tension: effects;

;. "The itreated ,blacksi eontain; and;

0 amount of the treating acid, such thatdt zmafibe "difficultljor', impossibleyto identify the presence of the-.a'cid byiordinary analytical'itests;

Nevertheless p the; ,;-treated fblacks have fmaterially thestandpoint of their dispersion in rubber; on

,e; acid. which we have, foundgparticularly I advantageous; asj-iaboye pointed outjis :hydrochlorie acid,;which' can;readily vbe used in: aque 5.0 5:

,obta'inedwith. the: use of alcohol solutions "I the 1acid,pparticularlyrwhen freshly prepared.

I ;One result ofitheacid treatment-of the care .ph ridioxidecphosphorimacid, arsenic acidphy-155 h 't The acids can in general be used in aqueous" I i N I solution ;of.;sl1itabler strength,f1'or exampleya p caseabeen foundsufllcient; 'SOmewhat'morethan 5:50 1Q%:0 ut ;rsprayedi th Q 'f q W v .L' thorough admixture: .1 Good results'have alsolbeen canting oil the supernatant Water and testing-- the sludge. In the case of the untreated blacks with a low pH value the treatment with acid acpossible. The treated blacks mix in more quickly and in a shorter time and with a lowering of the mill temperature as compared with the untreated blacks. The stearic acid used in tread stock compositions maybe milledin with the black but if it is desired to add it later it mills inmore quickly. The other powdered compounding ingredients mixed with the rubber cording to the present invention makes the pH value still lower; while inthe case of untreatedblacks with a high pH .value; the treatment according to the present invention reduces the pH figure in general to around 3 or less. For ex; ample, in the case of carbon blacksv treated ,with .1% hydrochloric acid in aqueous solution! the. pH value of impingement blacks of low pH value in an untreated state were further materially reduced; while. the pH. of certainimpingement bla,cks of higher pH; value were. reduced to a .great extent, forexample, to less,than. 3.

illustrating this reduction, in pH value by treatingthe. carbon blacks with .1% hydrochloric acid in aqueous solution, thefollowing instance is given;

In. the case of. a fast curingimpingementrubher black the pHrvalue was reduced. by thetreatmerit, in one. case from 5.10 to. 2.7.0. ThepH value of the treatedblack may be somewhatdif- :ferent when .freshly prepared .from its value :after standing for. awhile, due, perhaps. to. a further dissemination, or distribution of. the acid throughout the mass.

w The, improvedpropertiesof the. treated blacks of; the present invention make them particular- 1y advantageous :for use in compositions where 'effective'distribution or incorporation of the car-- bon. black is important. .merous instances that a more liquidproduct or composition was obtained with-the treated. black than with the sameblack untreated, when these respective blacks were incorporated in. rubber.

general the acidused in treating the black lshouldnot be of such a nature or-ins'uch-an amount asito be incompatible-with the particular composition or itsingredients with whichit isin- 'corporateds The new blackstherefore giveimprovedrubber compositions in: which the treated blacks 'are incorporated. i T .i

. xA valuable. embodiment andapplicatiom of the .presentinv-ention involves the utilization. of the new treated blacks in making tread stock compositions :having a-high carbon. black-content.

In the manufacture of. tire I treads for. automobiles it is customary to use-tread stock for- ,mulas. containing a high-percentage of carbon black, amounting toaround45 or 50% by weight, of therubber.inthecomposition. The difficulty in. obtaining a proper distribution or incorporation of the carbon black in therubberis well recognized, as well asthe .difliculty inobtaini'ng consistently uniform results. The treated blacks of. thepresent invention haveimproved properties which make them particularly valuable -foruse. in :such tread stock compositions. The treatment of 1 the black facilitates the dispersion or..incorporation of the black in the rubber and ,the plasticizing. of the. rubber. blacksrcan be readily incorporated with hard,

The treated unmilled. rubber. and. to. betteradvantage with rubber which .has been .somewhatzsoftened, but it not necessary. tomaintain .the. mix asz'stifiaa's i 75 We have found nurated, were indicated. bry-v visualaappearance and 5 for slightly; higher;

black ontherubben and: which.

composition can also be mixed more quickly when the new treated blacks are used. Much less time is also required to get good dispersion or incorporation and the resulting stocks rernill si r- 3 Testso'n. the vulcanized tread stock compositions show a very marked increase in the resistance to abrasion and in flexing properties, as well as a notableincrease in the modulus.

The. following composition illustrates a tire tread formula on which a series of cures were carried out:

In the above composition; both untreated carbon black and treated ca'rb'on black were used in different batches. in the batchescontaining the untreatedbIackBparts, of pine tar were used; and inthe batchescontaining treated black l part; of pine tar was used. Cures were madeiat 274? F. and with a series oftifne intervals, namely, ten, fifteen, thirty; forty-five, sixty ninety, and one hundred and twenty minutes. A study of the results showed that the sixty nnnutejcur'es reflect in 'a satisfactory way'the'cor'npa one between the various mixtures. g

Comparingthe sixty minute em-es thus obtain'ed with the formulas containing, untreated an treated blacklt was, that the treated 1 blacks Sh'QWfd a marked increase] in the 300% modulus and a,si'g'iiifl'cant jincrease theterisilee s'tr'ength atbreak, j W

With products face with the above, formula, anacompar mg the representative; any in me th ,50%;oi aarbonb la'cli ontne, iubbeijth' tensi e was 443mm the 300%, morning as 1600mm,- the, untreated a and. snowed an. increase witlitlieftreated tia'cxzoi r 'bni. 103m 15% the means. with the. ,esgrennriin i ey... the

Similar improved, re ults; were obtained; at;

"45.95am: so carton, man; on tiiarubbea, In

the. case-of a. "formulamade'with i 5 jcarbon g showed. a-tensile .15 twith themt iev ke erea e imd i 96. W854)??- i; E9 -d: 5.% WAS bta n d mstockszoontamins. %.carbc i;ma k-,... I i i he. m lor d ropertiescfi the rubbenroompositiflnin ,whicnthe ,rtreatedrblacks rwere. incorpowere further-. indicated; by consistently i better abrasion and. flexing results, 5. as compared with compositions containing; untreated blaoksimarkedzinorease inrmodulus; strikingly coil- I treated blacks.

firms the improved results obtained with the The results obtained with the I black treated with hydrochloric acid indicates I that for best results only a very small percentage of 1% of hydrochloric acid on the black is required. The blacks treated with hydrochloric acid may show some retarding of the sulting products to severe aging tests, the typical tread stock formulas showed comparable aging results in the two cases.

- includes the use of blacks with other ac ds with use oif carbon which similar but somewhat varying resultsare 7 obtained. In general, as above pointed out, the

' other acids can be used in quantities equivalent. 7

molecularly to 0.1% hydrochloric acid on the,

I black and about 0.05% on the rubber, inthecase' of tread stock'compositions containing about 50% carbon black based on the rubber. With the organic acids a somewhat larger amount of the acid may be desirable, including amounts several times thatequivalent molecularly to the hydrochloric acid, but in any event the percentage of the acid ,on the black is small, as previously indicated.

We claim: c 1

1. Rubber compositions containing a large proportion of an acid treated, impingement carbon black carrying an added water soluble acid," the amount of acid being less than 1% basedonthe black,qsaid carbon black having a, reduced pH 'It is one advantage of the treated carbon black I pigments of the present inventiomwhen used in tread stock compositions, that an increased amount of the black can be used and satisfactory dispersion or incorporation or admixture never-- theless obtained. Compositions containing from 45 up to 70% of the treated blacks have been satisfactorily produced. In its broader aspects, however, the percentage of the treated black used in the new rubber compositions is not limited to these proportions but lower amounts can be used, particularly for low carbon formulas,

and with improved results in the compounding and dispersion of the carbon blacks in the rubber.

The carbon blacks commonly used in rubber compounding for tread stocks are so-called channel blacks, although other impingement blacks are extensively usedi The carbon black used in the above examples was channel black.

As previously pointed out, we consider hydrochloric acid particularly advantageous for treating carbon blacks for rubber compounding; and the improved results obtained are indicated by the above examples and particularly by the materially increased modulus obtained.

value and improved properties as compared with I the untreated carbon black.

2. Rubber compositions containing a largeproportion of an acid treated, impingement carbon black carrying a fraction of 1% of hydrochloric acid and having a reduced pH value as compared with the untreated carbon black.v

3. Rubber tread stock compositions'made with a large proportion of an acid treated, impingement carbon black carrying a fraction of 1% "of,

hydrochloric acid and having a reducedpH value I as compared with the untreated carbon black.

I 4. The method or producing rubber composit tions which comprises incorporating therein an In its broader aspects, however, the'invention acidtreated-impingement carbon bia'cl; carrying an added water soluble acid, the amount ofacid I being less than 1% basedon the black, said carbon black having a reduced pH value and improved properties as compared black.

5. The method of producing rubber composi tions which comprises incorporating therein an;

acid treated, impingement carbon black carrying a fraction of 1% of hydrochloric, acid and having a reduced pH value as compared with the untreated carbon black. 7

ROBERT J. KING. 1 WILLIAM MITCHELL, J3, I

with theuntreate'd carbon I 

